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Americium

physical science Maturity 11-13 Next article →

Americium is a synthetic chemical element with the symbol Am and atomic number 95. It is a radioactive, transuranic member of the actinide series. This means it is an element heavier than uranium. On the periodic table, it is located directly below the lanthanide element europium. Because of this specific position, scientists named it after the Americas. Americium appears as a relatively soft, silvery metal.

Closest packing ABAC
Closest packing ABAC

In chemical compounds, it usually assumes an oxidation state of +3. However, it can exist in other states ranging from +2 to +7. These different states can be identified using optical absorption spectra.

The production of americium is a complex nuclear process. Most americium is created in nuclear reactors by bombarding uranium or plutonium with neutrons. It is not synthesized directly from uranium. Instead, it begins with the isotope plutonium-239. This isotope must first capture a neutron to become uranium-239. This uranium then undergoes beta decay to become neptunium-239. After a short time, the neptunium undergoes another beta decay to become plutonium-239. To reach americium, the plutonium-239 must capture two more neutrons to become plutonium-241. This plutonium-241 then undergoes beta decay to finally become americium-241.

Elutionskurven Tb Gd Eu und Bk Cm Am
Elutionskurven Tb Gd Eu und Bk Cm Am

Scientists have identified several different isotopes of this element. The most common and longest-lived isotopes are americium-241 and americium-243. Americium-241 has a half-life of 432.2 years. Americium-243 is even more stable, with a half-life of 7,350 years. There are also shorter-lived isotopes like americium-242. This isotope has a half-life of only about 16 hours. In a light water reactor, 79% of americium-241 converts into americium-242. A small amount, about 10%, becomes a nuclear isomer known as 242mAm. This isomer is very interesting to researchers but is currently quite scarce and expensive.

The history of americium is tied to major scientific milestones. It was first intentionally synthesized and identified in late 1944. A research group led by Glenn T. Seaborg worked on this discovery. The team included Leon O. Morgan, Ralph A. James, and Albert Ghiorso. They performed their work at the University of California, Berkeley, and the Metallurgical Laboratory in Chicago. They used a massive 60-inch cyclotron to aid their experiments.

Berkeley 60-inch cyclotron
Berkeley 60-inch cyclotron

Because this work was part of the Manhattan Project, the discovery remained a secret. It was not released to the public until November 1945. Seaborg actually leaked the news on a radio show for children before the official presentation.

Americium has several important industrial and commercial uses. One of its most common applications is in commercial ionization chamber smoke detectors. It is also used as a neutron source and in various industrial gauges. Scientists have proposed using the isotope 242mAm for more advanced technology. This could include nuclear batteries or fuel for spaceships using nuclear propulsion. However, these uses are currently limited by the high cost of the material. The separation process required to get pure americium is extremely painstaking and difficult.

While americium is mostly man-made, it can be found in specific environments. It was detected in the fallout from the Ivy Mike nuclear test.

Ivy Mike - mushroom cloud
Ivy Mike - mushroom cloud

It is also found at sites of nuclear incidents, such as the Chernobyl disaster. Trinitite, the glass formed during the Trinity test in New Mexico, contains traces of americium-241. In most natural soil, americium levels are very low. It tends to adhere to soil particles rather than dissolving in water. In sandy soil, the concentration in particles can be 1,900 times higher than in the surrounding water.

Understanding americium is vital for managing nuclear waste. One tonne of spent nuclear fuel contains about 100 grams of americium. Because americium is long-lived and radioactive, it is undesirable for long-term waste disposal. Scientists are working on a process called nuclear transmutation. This involves separating the americium and bombarding it with neutrons in special reactors. This process aims to convert the long-lived americium into shorter-lived nuclides. This research helps make the management of nuclear materials safer for the future.

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🖼️ Images & Media (4)
File:Berkeley 60-inch cyclotron.jpg
Berkeley 60-inch cyclotron.jpg
File:Ivy Mike - mushroom cloud.jpg
Ivy Mike - mushroom cloud.jpg
File:Elutionskurven Tb Gd Eu und Bk Cm Am.png
Elutionskurven Tb Gd Eu und Bk Cm Am.png
File:Closest packing ABAC.png
Closest packing ABAC.png
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